In signal processing applications, a sampling rate (also known as sample rate or sampling frequency) defines the number of samples per second (or other unit) taken from a continuous signal to make a discrete signal. In some applications, it is desirable to modify a sampling rate of a digital signal. For example, audio may be recorded at a first sampling rate to create a digital representation of the audio, and a device (e.g. a CD player, mp3 player, or the like) may output audible sounds based on the digital representation at a second sampling rate. In this scenario, the first sampling rate of the digital representation may need to be converted to the second sampling rate expected by the device. In another example, where a device may be used to overlay or simultaneously output an audible sound based on two or more digital representations, sampling rates of the two or more digital representations may need to be matched for simultaneous playback.
In order to convert a sampling rate of a digital signal, many electronics devices employ one or more sampling rate converters (SRC). An SRC receives a digital input signal, up and/or down-converts the signal, and outputs a digital output signal with an adjusted sampling rate. Typical SRCs employ a static conversion ratio regardless of a sampling rate of digital input or output signals.
Streaming of data, such as an audio data signal, has become commonplace in many electronics applications. For example, instead of playing stored music, many systems and devices are operable to transmit a digital signal which is then played back as it is received by a device, such as a mobile device. In streaming applications, it may be important to synchronize a clock of the incoming signal with a clock of the device on which the signal is received. For example, a mobile device may receive a radio or other signal at a first clock rate, while the mobile device itself may operate on a second, different clock rate based on a clock local to the mobile device. If these clocks are out of sync, playback quality of the digital signal (e.g. audio playback of an audio signal), may suffer.
In order to synchronize a clock of a received digital signal to a local clock, many electronics devices employ one or more highly accurate clock generating devices or modules, for example a phase lock loop (PLL), to generate the local clock. A PLL may output a highly stable clock signal for synchronization. However a PLL may be expensive, take up a large amount of available space within a device, and/or consume a large amount of power relative to other electronics components. A highly accurate clock signal may be utilized as a reference to synchronize an incoming data signal. The highly accurate clock may also be utilized as a reference for other circuitry, such as a digital-to-analog converter that is utilized to convert a received digital signal to a useable form, e.g. an analog waveform that may be output as audible sound.